#include<iostream>
using namespace std;
class Factory(){
    public:
    static long long total;
    static void addProduction(long long items){
        if(items<0){
            cout<<"Invalid Production";
            exit(0);
        }
        total+=items;
    }
};
long long Factory::total=0;
int main(){
    int n;
    cin>>n;
    long long items;
    for(int i=0;i<n;i++){
        cin>>items;
        Factory::addProduction(items);
    }
    cout<<Factory::total;
    return 0;
}